1. Field of the Invention
The present invention relates to the field of the characterization and/or control of zones of temporal fluctuations of a scene.
More precisely, it relates to a method and to a device for the characterization and/or control of zones of temporal fluctuation of a scene, implementing an image processing system.
It applies to the characterization and/or to the control of flames, for example in a furnace, especially an industrial furnace, or in any other type of environment.
The invention can also be applied to other characteristics of industrial furnaces.
In general, the invention makes it possible to characterize, on the basis of a video signal arising from a positionally fixed camera, the zones of temporal fluctuations of a flame or of a scene in a furnace. The invention makes it possible among other things to distinguish and/or to separate the zones of temporal fluctuations from the static zones.
2. Description of the Related Art
The control of the thermal state of an industrial furnace is ordinarily carried out by the use of a small number of sensors. The sensors commonly employed are gas bleed systems which allow the characterization of the composition of the smoke and/or thermocouples which offer a measurement of the local temperature of the walls of the furnace or of the charge, and/or sensors which carry out a spectroscopic measurement of the combustion along an optical axis (termed “line-of-sight”) for flame control or monitoring purposes (safety).
However, the temperature sensors present in a furnace, on account of their small number, cannot always provide information about the drifting of the flame characteristics over time The absence of detection of a flame which does not conform through its geometry, length or position may result in premature wear of the refractory walls of the furnace, degraded quality of the product made, and the emission of pollutants beyond the limits of the environmental standards.
Video cameras are sometimes used on industrial furnaces in order to afford the operators a view of the interior of the furnace. The quality of the visual information is nevertheless limited by the strongly fluctuating nature of the flame, due to turbulence, and by the subjective character of the interpretation.
Commercial computerized systems have very recently appeared which offer continuous tracking of the flame through analysis of video images. These flame characterization systems, however, do not make it possible to remedy the above mentioned problems.
Patent U.S. Pat. No. 5,249,954 describes an analysis, by a CCD sensor, of the chemiluminescence of the flame, in association with a neural network, for correlating various chemiluminescence fields with the ratio of oxidant/fuel flow rates. Here again, this type of device does not make it possible to provide information about the drifting of the characteristics of the flames over time.
Patent U.S. Pat. No. 5,971,747 describes an automated system for controlling combustion, which implements video cameras, image processing by a neural network, and a fuzzy logic control system. It is combined with other types of sensors, such as photodetectors, temperature sensors or pressure sensors. Such a system is very complex and does not make it possible to solve the problems of the wearing of the walls, of the degraded quality of the product made and of the emission of pollutants related to the drifting of the characteristics of the flames over time.
Finally, none of these known techniques is compatible with characterization and/or regulation of a flame, outside a furnace, for example in the open air.
Neither are any techniques known which can be applied to the characterization and/or to the control of temporal fluctuations of a scene of an industrial furnace, such as for example the charge of a furnace.